Diporous cation-covalent organic framework materials, their preparation methods, ratiometric fluorescent probes, and applications.

Abstract

This invention relates to the field of fluorescence sensing materials technology, specifically to a biporous cationic covalent organic framework material, its preparation method, a ratiometric fluorescent probe, and its applications. The unit cell parameters of the biporous cationic covalent organic framework material are: a = 72.3305 Å, b = 72.3305 Å, c = 3.7877 Å, α = β = 90.000°, γ = 120.000°; its structure is shown in Formula I. This invention utilizes the strong electrostatic interaction between the nanoscale pore wall ion sites of the biporous cationic covalent organic framework material and the charged groups of fluoroquinolone antibiotics, combined with a spatial matching effect, to achieve highly selective recognition of FQs.

Description

Technical Field

[0001] This invention relates to the field of fluorescence sensing materials technology, specifically to a two-porous cationic covalent organic framework material, its preparation method, the ratiometric fluorescent probe constructed therefrom, and its application in the detection of fluoroquinolone antibiotics. Background Technology

[0002] Fluoroquinolones (FQs), with their broad-spectrum antibacterial properties, are widely used in livestock and aquaculture for disease prevention and growth promotion. However, with the overuse and indiscriminate discharge of these antibiotics, FQ residues accumulate in environmental media such as soil and water. This can not only induce the spread of bacterial resistance genes, triggering a "superbug" crisis, but also threaten the human immune system and disrupt endocrine function through the food chain, and even damage the structure of aquatic organisms and soil microbial communities, endangering ecosystem stability. Therefore, establishing efficient and accurate quantitative detection methods for FQs in the environment is of vital practical significance for ensuring ecological security and human health.

[0003] Fluorescence detection technology, as an analytical method based on the fluorescence properties of substances, has been widely used in many fields such as life sciences, environmental monitoring, and materials science. However, in the detection of fluorescence quantifiers (FQs), traditional fluorescent probes, such as single fluorescent probes and molecularly imprinted polymer fluorescent sensors, have several shortcomings: First, insufficient selectivity; complex matrix components in the environment, such as metal ions and organic matter, easily interact non-specifically with the probe, leading to false positive results and affecting the accuracy of detection. Second, weak anti-interference ability; single fluorescence signals are easily affected by factors such as pH value, photobleaching, and background fluorescence, resulting in poor detection stability. Third, limited sensitivity; the interaction mechanism between traditional probes and FQs is relatively simple, mainly relying on weak interactions such as hydrogen bonding and π-π stacking, making it difficult to achieve effective detection of low concentrations of FQs. Summary of the Invention

[0004] Based on the above-mentioned technical problems, the present invention provides a dual-pore cationic covalent organic framework material, which utilizes the strong electrostatic interaction between the ionic sites on the nanoscale pore wall and the charged groups of fluoroquinolone antibiotics (FQs), combined with the spatial matching effect, to achieve highly selective recognition of FQs.

[0005] Furthermore, this invention focuses on constructing a ratiometric fluorescent probe based on this dual-porous cationic covalent organic framework material. By controlling the ion site density and fluorescent group type in the material framework, a synergistic mechanism of "ion electrostatic interaction-fluorescence signal response" is established. This probe utilizes the ratio of dual-wavelength signal intensity to eliminate interference from single signals, enabling rapid, sensitive, and intuitive detection of fluorescein ions (FQs) in various water bodies, thus improving detection accuracy and practicality. It exhibits a good linear relationship with FQ concentration in the concentration range of 5–50 μM, R0 2 恩诺沙星 =0.9706, R 2 环丙沙星 =0.9753, the detection limit of enrofloxacin (ENR) is as low as 2.29 μM, and the detection limit of ciprofloxacin (CIP) is as low as 1.01 μM.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is to provide a biporous cationic covalent organic framework material with the following cell parameters: a = 72.3305 Å, b = 72.3305 Å, c = 3.7877 Å, α = β = 90.000°, γ = 120.000°; the structure of the biporous cationic covalent organic framework material is shown in Formula I. .

[0007] The described biporous cationic covalent organic framework material (COF) is linked to an organic aromatic cyclopyrene structural unit via dynamic covalent imine bonds using a pyridinium salt as a linker, exhibiting good structural stability. This COF material uniformly embeds a large number of pre-designed pyridinium ion sites into the channel walls of nanoscale COFs, creating aligned but spatially confined ion interfaces. These interfaces can generate strong electrostatic interactions with specific structures in guest molecules of fungible molecule (FQs), effectively enhancing the affinity and selectivity of COFs for FQs. Simultaneously, the pyrene and pyridinium functional groups on the surface of the COF material facilitate further interactions with FQs through π-π and hydrogen bonds.

[0008] In a preferred embodiment of the present invention, the biporous cationic covalent organic framework material is a thin-layer nano-strip structure with a diameter in the range of 90 to 120 nm.

[0009] The second technical solution of the present invention provides a method for preparing the aforementioned diporous cationic covalent organic framework material, comprising the following steps: Under an inert gas atmosphere, 1,3,6,8-tetrakis(4-formaldehyde phenyl)pyrene and 1,1'-bis(4-aminophenyl)-4,4'-dichlorinated bipyridine are mixed evenly in an organic solvent and then immersed at room temperature to carry out a polycondensation reaction, thereby obtaining a biporous cationic covalent organic framework material.

[0010] In a preferred embodiment of the present invention, the polycondensation reaction is carried out at room temperature and in an inert gas atmosphere for 1 to 3 days.

[0011] More preferably, the reaction time of the polycondensation reaction is 1 day.

[0012] More preferably, the inert gas atmosphere is a nitrogen atmosphere.

[0013] In a preferred embodiment of the present invention, the molar ratio of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene to 1,1'-bis(4-aminophenyl)-4,4'-bipyridine dichloride is 1:1 to 2.

[0014] In a preferred embodiment of the present invention, the organic solvent is selected from one or more of tetrahydrofuran, 1,4-dioxane, mesitylene, o-dichlorobenzene, ethanol, o-dichlorobenzene, n-butanol and N,N-dimethylacetamide.

[0015] More preferably, the catalyst used in the polycondensation reaction is an acetic acid solution, and the concentration of the acetic acid solution is 3-6 M, and the volume ratio of the organic solvent to the acetic acid catalyst is 10-20:1.

[0016] As a preferred embodiment of the present invention, the reaction further includes a step of performing a freeze-pump-thaw cycle degassing treatment on a mixed solution of 1,3,6,8-tetra(4-carboxyphenyl)pyrene, 1,1'-bis(4-aminophenyl)-4,4'-dichlorinated bipyridine and an organic solvent, followed by sealing.

[0017] More preferably, the freezing-pump-thawing cycle degassing process is carried out in an N2 liquid bath to create an inert N2 atmosphere for the heating reaction.

[0018] As a preferred embodiment of the present invention, a post-processing operation is also included, specifically: after the reaction is completed, the precipitate is collected by filtration, the precipitate is washed several times with tetrahydrofuran and methanol in sequence, and finally the precipitate is dried under vacuum to obtain the diporous cationic covalent organic framework material.

[0019] The third technical solution of the present invention is to provide a ratiometric fluorescent probe, which is constructed from the aforementioned diporous cationic covalent organic framework material.

[0020] In a preferred embodiment of the present invention, the biporous cationic covalent organic framework material is ultrasonically dispersed in a Tris-HCl buffer solution to obtain a biporous cationic covalent organic framework material fluorescent probe.

[0021] Furthermore, the Tris-HCl buffer solution has a concentration of 50 mM and a pH of 7.

[0022] The fourth technical solution of the present invention provides an application of the ratiometric fluorescent probe in the detection of fluoroquinolone antibiotics (FQs).

[0023] The above-mentioned ratiometric fluorescent probe exhibits good fluorescence stability. After the addition of FQs, the fluorescence at 420 nm is enhanced, while the fluorescence at 550 nm remains unchanged. Its fluorescence intensity ratio (I0.05) is [missing value]. 420 / I 550 The concentration of FQs showed a good linear relationship.

[0024] In a preferred embodiment of the present invention, the process of detecting FQs by the ratiometric fluorescent probe is specifically as follows: Different volumes of FQs standard solution were added to the ratiometric fluorescent probe to obtain a series of mixed dispersions with known FQs concentrations. After the reaction was complete, the fluorescence intensity ratio was measured at an excitation wavelength of 320 nm to obtain the relationship between FQs concentration and fluorescence intensity ratio. The sample to be tested is added to the ratiometric fluorescent probe, the ratio of fluorescence intensity of the sample to be tested at an excitation wavelength of 320 nm is measured, and the concentration of FQs in the sample to be tested is calculated using the relationship.

[0025] In a preferred embodiment of the present invention, the relationship between the enrofloxacin standard solution and the fluorescence intensity ratio is: Y 恩诺沙星 = -8.917X + 0.7866, correlation coefficient is R 2 恩诺沙星 =0.9706; the relationship between the ratio of ciprofloxacin standard solution to fluorescence intensity is: Y 环丙沙星 = -20.123X + 1.6277, correlation coefficient is R 2 环丙沙星 =0.9753, where Y is the fluorescence intensity ratio I. 420 / I 550 X represents the concentration of FQs.

[0026] This invention employs a relatively simple method to rapidly prepare a novel biporous cationic covalent organic framework material. The building units of this covalent organic framework material are connected by dynamic covalent imine bonds, resulting in good structural stability. Fluorescent probes designed using this material are rich in high-density pyridine groups and exhibit advantages such as fast response speed, high sensitivity, and intuitive detection results for anionic FQs drugs.

[0027] The biporous cationic covalent organic framework (COF) material provided by this invention is prepared by a Schiff base reaction of a diamine monomer containing a pyridyl functional group and a tetraaldehyde monomer containing a pyrene group under solvothermal conditions. This reaction utilizes a mild and simple room-temperature reaction system, avoiding complex heating processes and simplifying post-processing steps, thereby achieving high-yield preparation of materials with excellent chemical stability, laying the foundation for subsequent applications. The precise internal geometry of COFs provides uniform 1D diffusion channels, while the rigid nanochannels with spatial confinement effects also inhibit large-scale dendrite formation. The uniformly distributed ion sites, suitable pore size, and functional groups (pyridyl and pyrene) of COFs enable fluorescent probes constructed from them to sensitively detect fluorescein ions (FQs). Furthermore, the inherent fluorescence emission peaks of COFs can also serve as reference peaks, improving detection accuracy.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The biporous cationic covalent organic framework material prepared by this invention has unique structural features and excellent performance. First, the functional groups are highly ordered distributed along the pore walls of COFs to form ionic interfaces, which effectively promotes the interaction between the target analyte and the ionic sites and provides a rapid diffusion kinetic mode. Second, the pyridyl ions embedded in the one-dimensional channels of COFs endow the material with specific binding sites, and the generated charged functional sites can provide strong electrostatic and hydrogen bonding forces, which significantly enhances the interaction between COFs and FQs, effectively improves the detection sensitivity, and makes this material have important application potential in the field of FQs detection.

[0029] (2) The process for preparing biporous cationic covalent organic framework materials according to this invention has significant advantages. The process is simple and highly operable; operators can easily master and execute the relevant steps in actual production. Simultaneously, the sample yield is relatively high, meeting the needs of large-scale production. The reaction conditions are easy to achieve, requiring no extreme temperatures or pressures, and can be carried out in conventional experimental or production environments. Furthermore, this preparation method has low equipment requirements, eliminating the need for expensive or complex specialized equipment, which significantly reduces production costs, making the preparation of this material economical and practical, and facilitating its promotion and application in industrial production.

[0030] (3) The ratiometric fluorescent probe prepared using this invention has excellent detection performance. On the one hand, it can effectively eliminate interference from factors such as instruments and environment. The inherent fluorescence emission peak of COFs can be used as a reference peak. By comparing and calibrating with the detection signal, the influence of factors such as instrument fluctuations and environmental changes on the detection results can be reduced, thereby improving the accuracy of detection and making the detection results more reliable. On the other hand, the ratiometric fluorescent probe does not affect the detection effect under the interference of other types of antibiotics, showing good anti-interference ability. This means that even in complex sample environments, even if other antibiotics are present, the probe can accurately detect FQs, ensuring the specificity and accuracy of detection, and providing an efficient and reliable method for the detection of FQs. Attached Figure Description

[0031] Figure 1 This is the X-ray powder diffraction (PXRD) pattern of the cationic covalent organic framework material prepared in Example 1.

[0032] Figure 2 These are schematic diagrams of the AA lattice stacking model and the AB lattice stacking model.

[0033] Figure 3 The Fourier transform infrared spectra of the cationic covalent organic framework material and the raw materials 1,1'-bis(4-aminophenyl)-4,4'-bipyridine dichloride and 1,3,6,8-tetra(4-carboxyphenyl)pyrene prepared in Example 1 are shown.

[0034] Figure 4 This is a thermogravimetric analysis (TGA) diagram of the cationic covalent organic framework material prepared in Example 1 under a nitrogen atmosphere.

[0035] Figure 5 This is a scanning electron microscope image of a cationic covalent organic framework material.

[0036] Figure 6 The images show the X-ray photoelectron spectrum and the high-resolution spectra of the corresponding elements of the cationic covalent organic framework material prepared in Example 1, where a is the X-ray photoelectron spectrum, b is the high-resolution spectrum of C1s, c is the high-resolution spectrum of N1s, and d is the high-resolution spectrum of O1s.

[0037] Figure 7 In Figure a, COFs are the fluorescence emission spectra of enrofloxacin (ENR) in Tris-HCl buffer solution (λ = 320 nm) from 5 to 50 μM. Figure 7 b is I 420 / I 550 Linear relationship with enrofloxacin (ENR) concentration.

[0038] Figure 8In Figure a, COFs are the fluorescence emission spectra of 5–50 μM ciprofloxacin (CIP) in Tris-HCl buffer solution (λ = 320 nm). Figure 8 b is I 420 / I 550 Linear relationship between ciprofloxacin (CIP) concentration and concentration.

[0039] Figure 9 In the determination of 50 μM ciprofloxacin (CIP), different interfering substances were added. 420 / I 550 Change diagram Figure 9 In the middle b, different interfering substances were added when measuring 50 uM enrofloxacin (ENR). 420 / I 550 Change diagram. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] Based on research on diporous cation covalent organic framework materials, and combining their unique structure and properties, this invention aims to propose a more efficient and accurate ratiometric fluorescent probe design strategy to achieve highly sensitive and interference-resistant detection of FQs in the environment, filling the gap in the accurate detection of FQs in complex matrices in existing technologies.

[0046] All raw materials used in the specific embodiments of this invention are commercially available products. Among them, 1,3,6,8-tetrakis(4-formaldehydephenyl)pyrene has the CAS number 1415238-25-3, and its structural formula is shown below: ; The CAS number for 1,1'-bis(4-aminophenyl)-4,4'-bipyridine dichloride is 222973-24-2, and its structural formula is shown below: ​​.

[0047] In the specific embodiments of the present invention, room temperature specifically refers to 20~30℃.

[0048] Example 1 Preparation of biporous cationic covalent organic framework materials: 0.1 mmol of 1,3,6,8-tetra(4-formaldehydephenyl)pyrene, 0.2 mmol of 1,1'-bis(4-aminophenyl)-4,4'-dichlorobipyridine, and 10 ml of tetrahydrofuran were added to a Schlenk tube. The mixture was then sonicated for 15 minutes to ensure thorough mixing, and 1 ml of 3M acetic acid solution was added as a catalyst. The tube was then degassed using three freeze-pump-thaw cycles (N2 liquid bath). The Schlenk tube was then sealed and left to soak at room temperature without stirring for one day. Finally, the resulting grass-green powder was collected by centrifugation and washed twice alternately with N,N-dimethylformamide and tetrahydrofuran. The resulting grass-green powder was dried overnight under vacuum at 60 °C to obtain a biporous cationic covalent organic framework material with a yield of 78.7%. The structural formula is as follows:

[0049] .

[0050] Example 2 Preparation of biporous cationic covalent organic framework materials: 0.1 mmol of 1,3,6,8-tetra(4-carboxymethylphenyl)pyrene, 0.1 mmol of 1,1'-bis(4-aminophenyl)-4,4'-dichlorobipyridine, and 10 ml of tetrahydrofuran were added to a Schlenk tube. The mixture was then sonicated for 15 minutes to ensure thorough mixing, and 1 ml of 3M acetic acid solution was added as a catalyst. The tube was then degassed using three freeze-pump-thaw cycles (N2 liquid bath). The Schlenk tube was then sealed and left to soak at room temperature without stirring for one day. Finally, the resulting grass-green powder was collected by centrifugation and washed twice alternately with N,N-dimethylformamide and tetrahydrofuran. The resulting grass-green powder was dried overnight under vacuum at 60 °C to obtain a biporous cationic covalent organic framework material with a yield of 76.7%.

[0051] Example 3 Preparation of biporous cationic covalent organic framework materials: 0.1 mmol of 1,3,6,8-tetra(4-carboxymethylphenyl)pyrene, 0.2 mmol of 1,1'-bis(4-aminophenyl)-4,4'-dichlorobipyridine, and 10 ml of tetrahydrofuran were added to a Schlenk tube. The mixture was then sonicated for 15 minutes to ensure thorough mixing, and 0.5 ml of 3M acetic acid solution was added as a catalyst. The tube was then degassed using three freeze-pump-thaw cycles (N2 liquid bath). The Schlenk tube was then sealed and left to soak at room temperature without stirring for 3 days. Finally, the resulting grass-green powder was collected by centrifugation and washed twice alternately with N,N-dimethylformamide and tetrahydrofuran. The resulting grass-green powder was dried overnight under vacuum at 60 °C to obtain a biporous cationic covalent organic framework material with a yield of 77.8%.

[0052] Example 4 Preparation of biporous cationic covalent organic framework materials: 0.1 mmol of 1,3,6,8-tetra(4-formaldehydephenyl)pyrene, 0.2 mmol of 1,1'-bis(4-aminophenyl)-4,4'-dichlorobipyridine, and 10 ml of o-dichlorobenzene were added to a Schlenk tube. The mixture was then sonicated for 15 minutes to ensure thorough mixing, and 1 ml of 6M acetic acid solution was added as a catalyst. The tube was then degassed using three freeze-pump-thaw cycles (N2 liquid bath). The Schlenk tube was then sealed and left to soak at room temperature without stirring for one day. Finally, the resulting grass-green powder was collected by centrifugation and washed twice alternately with N,N-dimethylformamide and tetrahydrofuran. The resulting grass-green powder was dried overnight under vacuum at 60 °C to obtain a biporous cationic covalent organic framework material with a yield of 76.9%.

[0053] Since examples 1-4 all yielded biporous cationic covalent organic framework materials with the expected effects of the present invention, the performance and effects of the biporous cationic covalent organic framework material will be described below using example 1 as an example.

[0054] 1. Characterization of biporous cationic covalent organic framework materials: Figure 1 The X-ray powder diffraction (PXRD) pattern of the cationic covalent organic framework material prepared in Example 1 is shown below. Figure 1 It can be seen that the main broad peak appears at approximately 2θ = 1.06° (001), indicating poor π-π packing between layers in the vertical direction. The calculated interlayer spacing is approximately 3.78 Å. Simulations using Material Studio suggest that COFs may exhibit two structural models: AA overlapping packing and AB staggered packing (illustrations of the AA lattice stacking model and the AB lattice stacking model are shown below). Figure 2 As shown, the left figure is the AA lattice stacking model, and the right figure is the AB lattice stacking model. Pawley refinement of the data yielded the following cell parameters: a = 72.3305 Å, b = 72.3305 Å, c = 3.7877 Å, α = β = 90.000°, γ = 120.000°, and relatively small values ​​for Rp (1.82%) and Rwp (2.56%).

[0055] Figure 3 The Fourier transform infrared (FTIR) spectra of the cationic covalent organic framework material prepared in Example 1 and the raw materials 1,1'-bis(4-aminophenyl)-4,4'-dichlorinated bipyridine and 1,3,6,8-tetra(4-carboxyphenyl)pyrene were compared. It was found that the obtained product exhibited a higher wavelength at 1633 cm⁻¹. -1 The characteristic peak at the (C=N bond) indicates that an imine bond is formed by the condensation of 1,1'-bis(4-aminophenyl)-4,4'-bipyridine dichloride with 1,3,6,8-tetra(4-carboxyphenyl)pyrene. Simultaneously, the NH group of the initial organic monomer 1,1'-bis(4-aminophenyl)-4,4'-bipyridine dichloride shows a peak at 3201 cm⁻¹. -1 The C=O of 1,3,6,8-tetra(4-carboxymethylphenyl)pyrene at 1699 cm⁻¹ -1 The disappearance of the characteristic peak also indicates that 1,1'-bis(4-aminophenyl)-4,4'-bipyridine dichloride reacted with 1,3,6,8-tetra(4-carboxyphenyl)pyrene in a Schiff base reaction to produce an imine bond.

[0056] Figure 4The thermogravimetric analysis (TGA) curve of the cationic covalent organic framework material prepared in Example 1 under a nitrogen atmosphere shows that the covalent organic framework material has high thermal stability, remaining stable up to approximately 300 °C. The material exhibits about a 3% mass loss at 142 °C, mainly due to the evaporation of residual organic solvents on the surface of the COFs. Above 300 °C, the mass loss increases rapidly, indicating that the framework structure begins to collapse. With further temperature increases, the material undergoes further carbonization and decomposition.

[0057] Figure 5 This is a scanning electron microscope image of a cationic covalent organic framework (COF). The COFs are thin-layered nanoribbon structures with a diameter of approximately 100 nm.

[0058] Figure 6 The X-ray photoelectron spectrum and corresponding high-resolution elemental spectra of the cationic covalent organic framework material prepared in Example 1 are shown, where a is the X-ray photoelectron spectrum, b is the high-resolution C1s spectrum, c is the high-resolution N1s spectrum, and d is the high-resolution O1s spectrum. The X-ray photoelectron spectrum shows four peak characteristics: C1s, O1s, N1s, and Cl2p. Figure 6 (a) The high-resolution C1s spectrum shows four independent peaks with binding energies of 284.28, 285.28, 286.08 eV and 287.68 eV, respectively. The chemical bonds corresponding to these peaks are -CC / C=C-, -CN-, -CO and -C=N-, respectively. Figure 6 (b) The N1s high-resolution spectrum shows two independent peaks with binding energies of 398.68 and 401.48 eV, respectively, corresponding to the chemical bonds -C=N- and -C=N-. + -( Figure 6 (c). The O1s high-resolution spectrum shows a single peak with a binding energy of 531.78 eV. The chemical bonds corresponding to the peak positions are -C=O ( Figure 6 (d).

[0059] Test case A ratiometric fluorescent probe constructed from a diporous cationic covalent organic framework material for FQs detection. (1) Preparation of fluorescent probes constructed from diporous cationic covalent organic framework materials 2.5 mg of the COFs prepared in Example 1 above was dispersed in a 50 mM Tris-HCl buffer solution with a pH of 7, and sonicated for 10 min to ensure uniform dispersion, resulting in a probe solution with a concentration of 0.05 mg / mL.

[0060] (2) Detection of FQs by fluorescent probes constructed from diporous cationic covalent organic framework materials Take 2 mL of probe solution and add different volumes of FQs standard solution (100 mg / L) to make the final FQs concentration 0–50 μM. After the FQs react fully with the probe stock solution, measure its fluorescence emission spectrum at an excitation wavelength of 320 nm. Establish the ratio of fluorescence intensity at wavelengths of 420 nm and 550 nm (Ig). 420 / I 550 The relationship between FQs concentration and FQs concentration was used to obtain a standard curve.

[0061] The results showed that within the concentration range of 5–50 μM FQs, I 420 / I 550 The concentration of enrofloxacin (ENR) and ciprofloxacin (CIP) showed a linear relationship with each other, and the ratio of FQs concentration to fluorescence intensity was I. 420 / I 550 Relationship: Y 恩诺沙星 = -8.917X + 0.7866, Y 环丙沙星 = -20.123X + 1.6277, with correlation coefficients R0 and R1 respectively. 2 恩诺沙星 =0.9706, R 2 环丙沙星 =0.9753, where Y is the fluorescence intensity ratio I. 420 / I 550 X represents the concentration of FQs. The detection limit for enrofloxacin (ENR) is as low as 2.29 μM, and the detection limit for ciprofloxacin (CIP) is as low as 1.01 μM. Figure 7 In Figure a, COFs are the fluorescence emission spectra of enrofloxacin (ENR) in Tris-HCl buffer solution (λ = 320 nm) from 5 to 50 μM. Figure 7 b is I 420 / I 550 Linear relationship with enrofloxacin (ENR) concentration. Figure 8 In Figure a, COFs are the fluorescence emission spectra of enrofloxacin (ENR) in Tris-HCl buffer solution (λ = 320 nm) from 5 to 50 μM. Figure 8 b is I 420 / I 550 Linear relationship between ciprofloxacin (CIP) concentration and concentration.

[0062] (3) Selective detection of FQs by fluorescent probes constructed from diporous cationic covalent organic framework materials Take several 2 mL aliquots of probe solution (concentration 0.05 mg / mL), and then add a certain volume of F to each aliquot sequentially. - Cl - SO4 2- NO3 - Na+ K + NH4 + Ca 2+ Mg 2+ Cr 3+ The system contained glucose, diclofenac sodium (DCF), bisphenol A (BPA), bisphenol B (BPB), sulfamethoxazole (SMT), and sulfamethoxazole (SIZ) standard solutions (all interfering substances were at a concentration of 50 μM). After the reaction was complete, the fluorescence emission spectra were measured, and the fluorescence intensity ratio was expressed as I. 420 / I 550 This serves as a basis for judging the impact of different interfering substances on fluorescence performance.

[0063] Figure 9 In the determination of 50 μM ciprofloxacin (CIP), different interfering substances were added. 420 / I 550 Change diagram Figure 9 In the middle b, different interfering substances were added when measuring 50 uM enrofloxacin (ENR). 420 / I 550 Change graph. Fluorescence intensity ratio I after adding different interfering substances. 420 / I 550 No significant changes were observed, indicating that it has good anti-interference ability.

[0064] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A biporous cationic covalent organic framework material, characterized in that, Its unit cell parameters are: a = 72.3305 Å, b = 72.3305 Å, c = 3.7877 Å, α = β = 90.000°, γ = 120.000°; the structure of the biporous cationic covalent organic framework material is shown in Formula I: 。 2. The diporous cationic covalent organic framework material according to claim 1, characterized in that, It has a nano-strip structure with a diameter of 90–120 nm.

3. A method for preparing the aforementioned diporous cationic covalent organic framework material, characterized in that, Includes the following steps: Under an inert gas atmosphere, 1,3,6,8-tetrakis(4-formaldehyde phenyl)pyrene and 1,1'-bis(4-aminophenyl)-4,4'-dichlorinated bipyridine are mixed evenly in an organic solvent and then immersed at room temperature to carry out a polycondensation reaction, thereby obtaining a biporous cationic covalent organic framework material.

4. The preparation method according to claim 3, characterized in that, The polycondensation reaction is carried out at room temperature in an inert gas atmosphere for 1 to 3 days.

5. The preparation method according to claim 3, characterized in that, The molar ratio of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene to 1,1'-bis(4-aminophenyl)-4,4'-bipyridine dichloride is 1:1 to 2.

6. The preparation method according to claim 3, characterized in that, The catalyst used in the polycondensation reaction is an acetic acid solution, and the concentration of the acetic acid solution is 3-6 M; The organic solvent is selected from one or more of tetrahydrofuran, 1,4-dioxane, mesitylene, o-dichlorobenzene, ethanol, o-dichlorobenzene, n-butanol, and N,N-dimethylacetamide.

7. The preparation method according to claim 3, characterized in that, The process also includes a post-processing step, specifically: after the reaction is complete, the precipitate is collected by filtration, and the precipitate is washed several times with tetrahydrofuran and methanol in sequence, and finally dried under vacuum to obtain the diporous cationic covalent organic framework material.

8. A ratiometric fluorescent probe, characterized in that, It is obtained by ultrasonically dispersing the biporous cationic covalent organic framework material of claim 1 in a Tris-HCl buffer solution.

9. The ratiometric fluorescent probe according to claim 8, characterized in that, The Tris-HCl buffer solution had a concentration of 50 mM and a pH of 7.

10. The use of the ratiometric fluorescent probe of claim 8 or 9 in the detection of fluoroquinolone antibiotics.

Images